COMPARATIVE ULTRASTRUCTURAL STUDIES OF SPERMATOGENESIS IN THE METZGERIALES (HEPATOPHYTA) II. THE BLEPHAROPLAST OF BLASIA PUSILLA

As in other hepatics, the young spermatid of Blasia pusilla contains a well-developed blepharoplast comprising a four-layered multilayered structure (MLS) and two overlying dimorphic basal bodies. The asymmetrical spline (S₁ or upper stratum of the MLS) numbers 20 or 21 microtubules (MTs) at its anterior tip and reduces to eight at the posterior limit of the lamellar strip (LS). Behind this the shank of the spline is five or six tubules in width over most of its length, approximately one revolution of the circumference of the gamete. The three-microtubule spline aperture underlies the anterior basal body and like those of most hepatics, it is closed at its anterior end. The asymmetrical LS (approx. 2.0 μm in length) is characterized by a right-hand posterior notch which lies below the spline aperture at the region of the cartwheel configuration of the anterior basal body (ABB). The staggered dimorphic basal bodies overlap for approximately one third of their lengths. Both lie parallel to the long axis of the spline. As in other hepatics, the ABB (1.2 μm in length) is subapical and comprises an anterior hub extension with progressive rearward additions of lateral, dorsal and ventral triplets. Over most of its length (2.1 μm) the longer posterior basal body (PBB) consists of a distinct central hub and three ventral triplets. Transition zones of both basal bodies contain stellate configurations into which the two central axonemal MTs frequently extend. The blepharoplast of Blasia shows several features in common with leafy, simple thalloid and complex thalloid liverworts. Compared with the few Metzgeriales observed thus far, the LS is less elongate and the basal bodies less staggered. Dimensions of basal body components and spline dimensions, however, are comparable to those of most leafy and thalloid hepatics. Striking similarities with the complex thalloid liverworts include a posterior notch in the LS and a spline aperture three MTs wide.     

STUDIES OF SPERMATOGENESIS IN THE HEPATICAE : I. Ultrastructure of the Vierergruppe in Marchantia

Spermatids of the liverwort Marchantia polymorpha were shown by analysis of thin-sections to contain a four-layered organelle, the Vierergruppe, lying between the flagellar bases above and a subjacent mitochondrial body. The uppermost layer consists of parallel tubules structurally similar to those of the axoneme. Some of the tubules extend beyond the four-layered region to form a long ribbon-like appendage. The second layer consists of low, vertical, membranous fins connected by numerous short links to the tubules above. The third layer, limited above and below by two horizontal membranes, consists of vertical partitions, apparently continuous with the fins. The fourth and lowermost layer consists of narrow parallel tubules aligned beneath alternate partitions. The long axes of the lower three layers are parallel to each other and lie at an angle of 48° to the tubule axis of the uppermost stratum. A graphic representation of a three-dimensional scale model interpreting organelle structure is given. The Vierergruppe supersedes Dreiergruppe interpretation in most if not all of the bryophytes studied to date.     

ULTRASTRUCTURAL STUDIES OF SPERMATOGENESIS IN THE ANTHOCEROTALES. II. THE BLEPHAROPLAST AND ANTERIOR MITOCHONDRION IN PHAEOCEROS LAEVIS: LATER DEVELOPMENT

Chromatin condensation begins as the multilayered structure (MLS) in Phaeoceros reaches its maximally structured differentiation. As nuclear elongation and chromatin condensation proceed, the S_2–4 strata disappear, and the nuclear beak extends between the S₁ and the nearly spherical anterior mitochondrion. In a mature sperm the mitochondrion is elongate and lies completely anterior to the blunt front end of the nucleus. The 12 S₁ tubules extend over the anterior mitochondrion and nucleus, but their number becomes reduced to five at the level where the nucleus' midportion is constricted. The anterior ends of the S₁ tubules lie embedded in a rather conical osmiophilic crest. Flagellar insertion is restricted to the extreme anterior tip of the S₁ tubules. The locomotory apparatus in Phaeoceros is compared with that of other bryophytes.     

ULTRASTRUCTURAL STUDIES OF SPERMATOGENESIS IN THE ANTHOCEROTALES. I. THE BLEPHAROPLAST AND ANTERIOR MITOCHONDRION IN PHAEOCEROS LAEVIS: EARLY DEVELOPMENT

Electron microscopic examination of thin sections showed that the blepharoplast of a young spermatid of Phaeoceros consists of two side-by-side centrioles and an accumulation of osmiophilic, granular matrix at their proximal ends. Lying between these nearly parallel organelles is a dark-staining body that will later disappear at the onset of flagellogenesis. For a brief period the centrioles are oriented perpendicular to the nuclear surface so that the granular matrix at their proximal ends is confluent with the nuclear envelope; furthermore, the nucleoplasm immediately in front of the centrioles becomes densely staining. The multilayered structure (MLS) develops directly under the centrioles. It comprises a band of 12 microtubules (the S₁ stratum) and three lower strata (S_2–4) whose constitutent lamellae are oriented at an oblique angle to the S₁ axis. While the S₁ tubules grow rearward over the nucleus which forms a beak adjacent to the posterior end of the lamellar strata, the centrioles are transformed into basal bodies with the distal growth of the axonemes and the proximal growth of the central cartwheels and lowermost triplets. The proximal ends of the basal bodies and the S₁ tubules overlying the lamellar strata are invested with osmiophilic matrix that extends down to the S₂ layer and may temporarily occlude the lamellar plates. At the onset of nuclear elongation an anterior mitochondrion becomes situated close beneath the lamellar strata which extend laterally beyond the S₁ tubules.     

STUDIES OF SPERMATOGENESIS IN THE HEPATICAE : III. Continuity between Plasma Membrane and Nuclear Envelope in Androgonial Cells of Blasia

An ultrastructural study of late-stage androgonial cells of Blasia pusilla, a thallose liverwort, showed the nearly spherical nuclei often lying close or appressed to the cell walls. In some cells the two membranes comprising the nuclear envelope separated, the inner membrane continuing intact as a limiting boundary of the nucleus and the membrane on the outer, cytoplasmic side recurving away from the nucleus to continue without evident interruption around the periphery of the cell as the plasma membrane. It is believed that Blasia offers the first completely convincing demonstration of the heretofore problematic continuity of cytoplasmic membranes. A possible sequence of events leading to this unusual relationship between nucleus and cytoplasm is suggested. The sequence includes blebbing of the outer membrane of the nuclear envelope and subsequent membrane proliferation, apparent isolation of cytoplasmic ground substance, fusion of internal membrane with the ectoplast, and migration that finally brings the nucleus into flat contact with the wall. While this manifestation of membrane continuity may be anomalous, it is not presently considered the result of cell injury.     

TEMPERATURE EFFECTS ON THE KINETICS OF SPERMATOGENESIS IN THE MOUSE

The kinetics of spermatocyte differentiation in adult mice was measured under normal conditions, during maintenance at elevated temperatures and following experimental cryptorchidism. For these measurements the development of ³H-TdR labelled testis cells was followed by velocity sedimentation at unit gravity and the results were in agreement with those obtained by autoradiography. In the cryptorchid animals and those maintained at 32°C the kinetics of spermatogenesis during treatment was increased by at least 13% over control values. Smaller but significant increases in the kinetics of spermatogenesis were obtained at ambient temperatures of 28 and 30°C without any observable histological damage. The increased kinetics is believed to be a direct effect of temperature on testis cell development.     

SPERMATOGENESIS IN COLEOCHAETE PULVINATA (CHAROPHYCEAE): EARLY BLEPHAROPLAST DEVELOPMENT

Transmission electron microscopy of serial thin sections was used to reconstruct several early developmental stages of the blepharoplast in Coleochaete pulvinata spermatids. These were compared to published studies of blepharoplast development in Charales and the closest relatives of charophycean green algae among embryophytes, i.e., hornworts and liverworts. Bicentriolar centrosomes such as occur in bryophytes and fern allies were not observed in Coleochaete. Centriole replication in C. pulvinata was orthogonal as in Charales. The resulting two daughter centrioles were oriented perpendicularly and joined proximally by electron-dense material. Their orthogonal relationship was maintained throughout blepharoplast development by a massive, banded connective which appeared early. In spermatids of hornworts and liverworts, a multilayered structure (MLS) develops in association with two centrioles destined to become flagellar basal bodies. When the MLS of these lower land plants is sectioned at right angles to the long axis of the microtubular layer, the MLS is observed to lie beneath cross sections of both centrioles. In contrast, when developing MLSs of C. pulvinata and Charales are similarly sectioned, they occur beside a cross section of just one of the two centrioles. In C. pulvinata (as in other charophytes), MLS lamellae are oriented at a 90-degree angle to the long axis of the S₁ microtubules from the beginning. This contrasts with the 40–45 degree angle between the MLS lamellae and S₁ microtubules universally reported for archegoniates. In early C. pulvinata spermatids, spline microtubules are closely associated with an anterior mitochondrion having a low stromal density and few cristae. An anterior mitochondrion is typically associated with blepharoplast development in hornworts and liverworts, but has not previously been reported to occur in Coleochaete or any other charophycean alga. In Coleochaete, as in hornworts and liverworts, but unlike Charales, structure of mature blepharoplasts reflects early blepharoplast ontogeny. Very little change in positional relationships among blepharoplast components (flagella, connective, MLS) occurs during development. These character-state differences are of importance in cladistic analyses of charophycean algae and lower land plants.     

STUDIES IN THE EMBRYOLOGY OF COMPOSITAE. IV. THE TRIBE INULEAE

Embryology of Blumea malabarica, B. membranacea, Laggera pterodonta, Anaphalis busna and Vicoa auriculata has been studied. The anther is tetrasporangiate in all the members except in Blumea membranacea where it is bisporangiate. The anther tapetum is of the Periplasmodial type. Both tetrahedral and isobilateral pollen tetrads are found. Mature pollen grains are three-celled with thick spinous exine. The ovary is bicarpellary syncarpous and unilocular with a single basal ovule. In one instance in Blumea malabarica two ovules per ovary with a rudimentary septum separating them was observed. The single hypodermal archesporial cell functions directly as the megaspore mother cell. The embryo sac develops according to the Polygonum type. The synergids in Blumea malabarica are hooked while in other members they are pear shaped. There are three antipodal cells except in Blumea membranacea where they increase up to eight. Endosperm development in Blumea malabarica is of the Nuclear type while in Blumea membranacea and Laggera pterodonta it is of the Cellular type. One or two layers of endosperm persist up to maturity. Embryo development follows the Senecio variation of Asterad type. The embryological information of this tribe along with that of other tribes will be utilized in evaluating the interrelationships of the family Compositae in a later paper.     

COMPARATIVE STUDIES ON RESPIRATION : IV. THE EFFECT OF ETHER ON THE RESPIRATION OF WHEAT.

These experiments show that 7.3 and 3.65 per cent ether solutions cause an increase in respiration followed by a decrease. The results agree with those of Haas on Laminaria, of Gustafson on higher fungi, and of Mrs. Brooks on bacteria. They do not agree with the theory of Verworn that anesthesia is a kind of asphyxia and that it decreases respiration.     

金鱼精子发生中的拟染色质小体

拟染色质小体是性细胞特有的细胞器。本文报道:在金鱼精子发生过程中,精原细胞含有大量的拟染色质小体,在它上面不仅聚集着许多线粒体,而且有膜片层附着,其本身还会出现环孔和类似线粒体内嵴状结构。随着细胞的分化,拟染色质小体逐渐变少减小,直至消失。本文对拟染色质小体的形成方式与功能进行了讨论。     

THE INFLUENCE OF X-RAYS ON ORGANELLE INDUCTION AND DIFFERENTIATION IN GRASSHOPPER SPERMATOGENESIS

The effect of x-irradiation on grasshopper spermatogenesis was studied with the aid of light and electron microscopy. The insects were irradiated at the second instar prior to the presence of maturation stages and observed at the last instar and imago stages. Dosages of 100 to 600 roentgens were found to retard the differentiation of the nucleus and mitochondrial nebenkern in spermatids. Evidence is presented that irradiation causes a curtailment and disorganization in the differentiation of the nebenkern from mitochondria. The above doses also induced the formation of supernumerary centrioles, flagellar filaments and acrosomes; nuclear disorganization as well as pycnosis and fragmentation also occur. The nucleus appears to be drawn toward each radiation-induced supernumerary acrosome, with consequent multipolarity of the nucleus. Induction of a set of flagellar filaments is seen only where the centriolar structure is in contact with the nucleus. Details are given of an organelle, heretofore not described, that is composed of anastomosed and interwoven cytoplasmic strands.     

STUDIES IN THE QUERCUS UNDULATA COMPLEX. IV. THE CONTRIBUTION OF QUERCUS HAVARDII

Scrub oak populations in the semidesert area of northeastern Arizona and southeastern Utah are ordinarily identified in regional manuals as Quercus undulata. They are very similar, both morphologically and ecologically, to Q. havardii of the Staked Plain of the Texas Panhandle and southeastern New Mexico. They differ, however, in a number of inconspicuous characters. Population sample analyses indicate that most of these differences are suggestive of Q. gambelii, and the deviant populations are thus interpreted as having been derived from ancestral Q. havardii through introgression by Q. gambelii. Two differences are not in accord with this interpretation; these are regarded as possible cases of transgressive segregation. Considering the evolution of these hybridized populations, it is speculated that the ancestral Q. havardii occurred to the south and west of the present range of this species during the Kansan period of the Pleistocene. During subsequent northward dispersal, it became split in two. The eastern portion ultimately came to occupy the present range of the species in the Staked Plain; the western portion—lying to the west of a north-south mountain barrier in central New Mexico—became introgressed by Q. gambelii (and locally by Q. turbinella), resulting in the present populations of Arizona and Utah.     

中国齿裂菌属研究IV

报道我国齿裂菌属的5个分类单元,其中多角齿裂菌Coccomycesmultangularis Y.R.Lin & Z.Z.Lisp.nov.,中国齿裂菌C.sinensis Y.R. Lin&Z.Z.Lisp.nov.和山矾齿裂菌C.symploci Y.R.Lin & Z.Z.Lisp.nov.是新种,辐射状齿裂菌C.radiatusSherw.为中国新记录。提供了新种的拉丁文简介、汉文描述和形态特征图。模式标本存放在安徽农业大学森林保护教研室(AAUFP)。     

INDUCED APOSPORY IN THE LIVERWORT BLASIA PUSILLA

Immature sporophytes of Blasia pusilla L. collected in the field were excised from the protective gametophytic tissues and cultured on a slightly modified Knop's agar substrate in microphytotrons. Under the experimental conditions the setae elongated and after 33½ to 6 weeks many began to give rise to from 1 to 20 or more aposporous outgrowths. These subsequently developed into young gametophytes. The apices were then cut off, sterilized, and grown on glucose-mineral agar in aseptic culture. The resulting gametophytes were similar to haploid plants derived from spores in pattern and rate of growth, and in possession of rhizoids, ventral scales, lateral lobes, auricles, and stellate and discoid gemmae. They produced archegonia but no antheridia. The chromosome number of the aposporous plants was 18 in contrast to the normal haploid number of 9.     

STUDIES IN THE PHYSIOLOGY OF FOREST TREES. IV. MOISTURE MOVEMENT IN DECAPITATED STEMS

Greenidge , K. N. H. (Dalhousie U., Halifax, Nova Scotia.) Studies in the physiology of forest trees. IV. Moisture movement in decapitated stems. Amer. Jour. Bot. 47(10) : 816–819. Illus. 1960.—The rates and patterns of moisture movement in large, decapitated ring-porous stems have been investigated with the aid of water-soluble dyes injected into the lower boles of standing trees. A few observations have been made also in diffuse-porous trees treated in the same manner. Movement has been found to continue to the very apices of the stubs of oak and elm stems in the complete absence of foliar surfaces. Similar results were obtained in untouched stubs, and in stubs, the sawn surfaces of which were shellacked following decapitation and prior to injection. In oak and elm thus treated, maximum rates of movement approached 1/2 the velocities characteristic of entire stems. In shellacked and unshellacked stubs injected 20–24 hr. after decapitation, rates of movement, although commensurable, were further decreased. The relative distance moved by the stain varied on occasion in ash, and rates of movement dropped markedly in this species following decapitation. Similarly, speeds of travel were much reduced in diffuse-porous species following detopping.